From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8726E3C1090 for ; Sat, 4 Jul 2026 13:01:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783170072; cv=none; b=cHk39frMtJnw6w7fYQ8aNWfg6p1sfO2GIhiOpwA4RIwWaax4p9M8HA3zPFRnK6Yej1AwoqXmF1owU1tpZUtqSqk5+aQsIZyeikepJTLjc62Gq6R7Ubye2/ry5uOYLdKbzpADi7guEqxIkSyekvd3Fqi+p3rGgE9tvH4P6kxIXWE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783170072; c=relaxed/simple; bh=a9V/JPcvBqvePkdaMvSsBuYQjRAbIFXJgwrFmfF3aso=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=poZvLNOwstq/qP0qAbjkLi49S4M9OddwMCfI8DnX9aP51hQQD+6iXLI4mONGyjEgnqXfQVhhBA/Fp6uZzoLWqgcbVfM4CDipkpUjIFHVorc7NapTje2Yp+jyaBWrSZerWtzzI0AXu4NQjGQDi2seljkrgoWauqoWAIEF7P6b5vU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YzfpZVxe; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YzfpZVxe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3F501F00A3A; Sat, 4 Jul 2026 13:01:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783170071; bh=k5b8x32VmGjMOkLod0KV6qaPrD91tGyRAF8OyNJOapg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=YzfpZVxe8uxg0Glzhie+rCoC+tCRDhlBPZLUafrBBGs5VNokFu7S/kIZ2YTXOiEMw VpUdoN0tpW0kouY8IDNnGtaIjBlTvWiaja61vBo0t7Cdzq26ByY+NIEL94Z5/3FMEb 3ZAwuA64kTKdfSRTT6UITM+BpLcvzNiOZD0dE+BdSPjH2LbO7gO+H+X7tAislcuJ7F InVd+6sl6IQQ9PqnJitwWIQmpvbwPvmX+qEq2Jfw9Hy1UMMJFKWMJMfj0RI+pkKwlh ML6fzn8ABjVhrPw5aTicP0e60M0rwqwGBp+PtPvpll7EBWkyNS6wTOWNUe3KFXAovk WMkW3BuYFPIsw== From: Sasha Levin To: stable@vger.kernel.org Cc: Denis Arefev , Christoph Hellwig , Jens Axboe , Sasha Levin Subject: [PATCH 5.15.y] block: Avoid mounting the bdev pseudo-filesystem in userspace Date: Sat, 4 Jul 2026 09:01:09 -0400 Message-ID: <20260704130109.829039-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026070222-ducking-flanked-b10f@gregkh> References: <2026070222-ducking-flanked-b10f@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Denis Arefev [ Upstream commit f73aa66dffcb8e61e78f01b56163ec16a15d06d2 ] The bdev pseudo-filesystem is an internal kernel filesystem with which userspace should not interfere. Unregister it so that userspace cannot even attempt to mount it. This fixes a bug [1] that occurs when attempting to access files, because the system call move_mount() uses pointers declared in the inode_operations structure, which for the bdev pseudo-filesystem are always equal to 0. `inode->i_op = &empty_iops;` [1] BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0010) - not-present page PGD 23380067 P4D 23380067 PUD 23381067 PMD 0 Oops: 0010 [#1] PREEMPT SMP KASAN NOPTI CPU: 2 PID: 17125 Comm: syz-executor.0 Not tainted 6.1.155-syzkaller-00350-g84221fde2681 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:0x0 Call Trace: lookup_open.isra.0+0x700/0x1180 fs/namei.c:3460 open_last_lookups fs/namei.c:3550 [inline] path_openat+0x953/0x2700 fs/namei.c:3780 do_filp_open+0x1c5/0x410 fs/namei.c:3810 do_sys_openat2+0x171/0x4d0 fs/open.c:1318 do_sys_open fs/open.c:1334 [inline] __do_sys_openat fs/open.c:1350 [inline] __se_sys_openat fs/open.c:1345 [inline] __x64_sys_openat+0x13c/0x1f0 fs/open.c:1345 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 Found by Linux Verification Center (linuxtesting.org) with Syzkaller. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Link: https://lore.kernel.org/all/20131010004732.GJ13318@ZenIV.linux.org.uk/T/# Cc: stable@vger.kernel.org Signed-off-by: Denis Arefev Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260521072857.5078-1-arefev@swemel.ru Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/bdev.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/block/bdev.c b/block/bdev.c index ce7c20c2661793..e015fea1521e2b 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -459,16 +459,12 @@ EXPORT_SYMBOL_GPL(blockdev_superblock); void __init bdev_cache_init(void) { - int err; static struct vfsmount *bd_mnt; bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode), 0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT| SLAB_MEM_SPREAD|SLAB_ACCOUNT|SLAB_PANIC), init_once); - err = register_filesystem(&bd_type); - if (err) - panic("Cannot register bdev pseudo-fs"); bd_mnt = kern_mount(&bd_type); if (IS_ERR(bd_mnt)) panic("Cannot create bdev pseudo-fs"); -- 2.53.0